Optical network virtualisation has recently become a hot topic among the research community due to its potential to enable the shaping of the Infrastructure as a Service (IaaS) concept. A major challenge that arises of paramount importance when virtualising a network is the so called Virtual Network (VN) embedding problem. While this problem has been extensively treated for electrical networks, there is very little work regarding Virtual Optical Network (VONs) embedding. This paper addresses the VON embedding problem, giving an insight about the potential challenges and presenting solutions that allow to optimally solving this problem in dynamic network scenarios.